* { box-sizing: border-box; margin: 0; padding: 0; }
      html { min-height: 100%; scroll-behavior: smooth; }
      body { min-height: 100vh; display: flex; flex-direction: column; font-family: Arial, Helvetica, sans-serif; background: #f5f7fb; color: #1f2937; line-height: 1.6; }
      main { flex: 1; }
      a { color: inherit; text-decoration: none; }
      button { color: inherit; font: inherit; }
      [hidden] { display: none !important; }
      .container { width: min(1100px, 92%); margin: 0 auto; }
      a:focus-visible, button:focus-visible { outline: 3px solid #60a5fa; outline-offset: 3px; }

      header { position: sticky; top: 0; z-index: 1000; background: #fff; border-bottom: 1px solid #e5e7eb; }
      .navbar { position: relative; display: flex; align-items: center; justify-content: space-between; gap: 20px; padding: 18px 0; }
      .brand { color: #0f172a; font-family: "Brush Script MT", "Comic Sans MS", cursive; font-size: 2.2rem; font-weight: bold; white-space: nowrap; }
      .nav-links { display: flex; align-items: center; justify-content: flex-end; flex-wrap: wrap; gap: 10px; }
      .nav-links > a, .dropbtn { padding: 10px 14px; border-radius: 10px; color: #374151; font-size: .98rem; font-weight: 500; transition: background-color .2s ease, color .2s ease; }
      .nav-links > a:hover, .nav-links > a[aria-current="page"], .dropbtn:hover { background: #eff6ff; color: #2563eb; }
      .dropdown { position: relative; }
      .dropbtn { display: inline-block; }
      .dropdown-content { position: absolute; top: 100%; left: 0; z-index: 1000; display: none; min-width: 230px; overflow: hidden; background: #fff; border-radius: 14px; box-shadow: 0 10px 28px rgba(15, 23, 42, .14); }
      .dropdown-content a { display: block; padding: 12px 16px; color: #1f2937; text-align: left; transition: background-color .2s ease, color .2s ease; }
      .dropdown-content a:hover { background: #eff6ff; color: #1d4ed8; }
      .dropdown:hover .dropdown-content { display: block; }
      .menu-toggle { display: none; padding: 8px; background: none; border: 0; border-radius: 8px; cursor: pointer; }
      .menu-toggle span { display: block; width: 28px; height: 3px; margin: 5px 0; background: #0f172a; border-radius: 2px; }

      .hero { padding: 62px 0 30px; }
      .hero-card { padding: 38px; background: linear-gradient(135deg, #fff 0%, #eff6ff 100%); border: 1px solid #dbeafe; border-radius: 28px; box-shadow: 0 10px 30px rgba(15, 23, 42, .06); }
      .breadcrumb { display: inline-block; margin-bottom: 14px; color: #2563eb; font-size: .95rem; font-weight: 600; }
      .breadcrumb:hover { text-decoration: underline; }
      .hero h1 { margin-bottom: 12px; color: #0f172a; font-size: clamp(2rem, 4vw, 3rem); }
      .hero p { max-width: 870px; margin-bottom: 12px; color: #4b5563; font-size: 1.03rem; }
      .hero p:last-of-type { margin-bottom: 0; }
      .ai-notice { display: flex; align-items: center; gap: 12px; margin-top: 18px; padding: 14px 16px; background: #faf5ff; border: 1px solid #e9d5ff; border-radius: 14px; color: #6b21a8; font-size: .9rem; }
      .ai-notice .ai-review-badge { flex: 0 0 auto; }
      .ai-notice > span:last-child { display: flex; min-height: 38px; align-items: center; }

      section { padding: 18px 0 8px; }
      .section-title { margin-bottom: 8px; color: #0f172a; font-size: 1.85rem; }
      .section-subtitle { max-width: 860px; margin-bottom: 24px; color: #6b7280; }
      .course-unit-section { padding: 28px 0 8px; scroll-margin-top: 108px; }
      .unit-heading { margin-bottom: 24px; }
      .unit-label { display: inline-block; margin-bottom: 8px; color: #2563eb; font-size: .84rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
      .unit-heading .section-title { font-size: clamp(1.65rem, 3vw, 2.05rem); line-height: 1.25; }
      .unit-heading .section-subtitle { margin-bottom: 0; }
      .unit-divider { height: 1px; margin: 44px 0 14px; background: linear-gradient(90deg, transparent 0%, #d9e0e9 10%, #d9e0e9 90%, transparent 100%); }

      .prerequisite-accordion { overflow: hidden; background: #fff; border: 1px solid #bfdbfe; border-radius: 22px; box-shadow: 0 8px 24px rgba(15,23,42,.05); }
      .prerequisite-toggle { width: 100%; display: grid; grid-template-columns: minmax(0, 1fr) auto; align-items: center; gap: 20px; padding: 24px 28px; appearance: none; -webkit-appearance: none; background: #fff; border: 0; color: inherit; cursor: pointer; font: inherit; text-align: left; transition: background-color .2s ease; }
      .prerequisite-toggle:hover { background: #f8fbff; }
      .prerequisite-toggle[aria-expanded="true"] { background: #f8fbff; }
      .prerequisite-toggle:focus-visible { position: relative; z-index: 2; outline: 3px solid rgba(37,99,235,.3); outline-offset: -3px; }
      .prerequisite-toggle-copy { min-width: 0; }
      .prerequisite-toggle h2 { margin-bottom: 5px; color: #0f172a; font-size: clamp(1.45rem, 3vw, 1.9rem); }
      .prerequisite-toggle p { max-width: 820px; color: #64748b; }
      .prerequisite-question-count { display: block; margin-top: 6px; color: #475569; font-weight: 650; }
      .toggle-icon { position: relative; width: 38px; height: 38px; display: inline-flex; flex: 0 0 auto; align-items: center; justify-content: center; background: #eff6ff; border: 1px solid #bfdbfe; border-radius: 12px; color: #2563eb; transition: transform .22s ease, background-color .2s ease, border-color .2s ease; }
      .toggle-icon::before { width: 10px; height: 10px; border-right: 2px solid currentColor; border-bottom: 2px solid currentColor; content: ""; transform: translateY(-2px) rotate(45deg); }
      .prerequisite-toggle:hover .toggle-icon { background: #dbeafe; border-color: #93c5fd; }
      .prerequisite-toggle[aria-expanded="true"] .toggle-icon { transform: rotate(180deg); }
      .prerequisite-content { margin: 0 14px 14px; padding: 24px; background: #f5f9ff; border: 1px solid #bfdbfe; border-radius: 18px; }

      .coming-soon-section { padding: 28px 0 8px; scroll-margin-top: 108px; }
      .coming-soon-card { padding: 28px; background: #eef1f5; border: 1px solid #cbd5e1; border-radius: 22px; color: #475569; }
      .coming-soon-card .unit-label { color: #475569; }
      .coming-soon-card h2 { margin-bottom: 8px; color: #334155; font-size: 1.55rem; }
      .coming-soon-card p { max-width: 720px; color: #64748b; }
      .status-pill { display: inline-flex; align-items: center; min-height: 30px; margin-top: 14px; padding: 5px 11px; background: #d8dee7; border-radius: 999px; color: #334155; font-size: .8rem; font-weight: 800; }

      .topic-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 22px; }
      .topic-card { position: relative; display: flex; flex-direction: column; min-width: 0; padding: 24px; background: #fff; border: 1px solid #e5e7eb; border-radius: 22px; box-shadow: 0 8px 24px rgba(15, 23, 42, .05); transition: transform .2s ease, box-shadow .2s ease; }
      .topic-card:hover { transform: translateY(-4px); box-shadow: 0 12px 30px rgba(15, 23, 42, .08); }
      .topic-card h3 { margin-bottom: 10px; color: #111827; font-size: 1.14rem; line-height: 1.35; }
      .topic-card p { margin-bottom: 18px; color: #6b7280; font-size: .94rem; }
      .topic-links { display: flex; flex-direction: column; gap: 10px; margin-top: auto; padding-right: 52px; }
      .topic-links a { align-self: flex-start; color: #2563eb; font-size: .95rem; font-weight: 700; }
      .topic-links a:hover { text-decoration: underline; }
      .ai-review-badge { position: relative; width: 38px; height: 38px; display: inline-flex; align-items: center; justify-content: center; background: #f3e8ff; border: 1px solid #d8b4fe; border-radius: 11px; color: #6b21a8; font-size: .78rem; font-weight: 850; letter-spacing: .04em; cursor: help; }
      .card-ai { position: absolute; right: 24px; bottom: 17px; }
      .ai-review-badge::after { content: attr(data-tooltip); position: absolute; right: 0; bottom: calc(100% + 9px); z-index: 10; width: min(300px, 75vw); padding: 10px 12px; background: #111827; border-radius: 10px; color: #fff; font-size: .76rem; font-weight: 500; line-height: 1.4; letter-spacing: 0; opacity: 0; pointer-events: none; transform: translateY(4px); transition: .18s ease; }
      .ai-review-badge:hover::after, .ai-review-badge:focus::after { opacity: 1; transform: translateY(0); }

      .info-strip { display: grid; grid-template-columns: 1.2fr .8fr; gap: 22px; align-items: center; padding: 24px; background: #fff; border: 1px solid #e5e7eb; border-radius: 22px; box-shadow: 0 8px 24px rgba(15, 23, 42, .05); }
      .info-strip h2 { margin-bottom: 8px; color: #111827; font-size: 1.35rem; }
      .info-strip p { color: #6b7280; }
      .side-box { padding: 18px; background: #f8fafc; border: 1px solid #e5e7eb; border-radius: 18px; }
      .side-box h3 { margin-bottom: 10px; color: #111827; font-size: 1.05rem; }
      .side-box ul { display: grid; gap: 9px; margin: 0 0 0 20px; color: #475569; font-size: .94rem; }
      footer { margin-top: 60px; padding: 32px 0; background: #0f172a; color: #e5e7eb; }
      footer p { color: #cbd5e1; font-size: .95rem; }

      @media (max-width: 1000px) { .topic-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); } .info-strip { grid-template-columns: 1fr; } }
      @media (max-width: 950px) {
        .course-unit-section, .coming-soon-section { scroll-margin-top: 170px; }
        .navbar { flex-wrap: wrap; }
        .menu-toggle { display: block; margin-left: auto; }
        .nav-links { display: none; width: 100%; flex-direction: column; align-items: stretch; gap: 8px; padding-top: 12px; }
        .nav-links.active { display: flex; }
        .nav-links > a, .dropbtn, .dropdown { width: 100%; }
        .dropdown-content { position: static; display: none; min-width: 100%; margin-top: 6px; border: 1px solid #e5e7eb; border-radius: 10px; box-shadow: none; }
        .dropdown:hover .dropdown-content { display: none; }
        .dropdown.mobile-open .dropdown-content { display: block; }
      }
      @media (max-width: 680px) {
        .topic-grid { grid-template-columns: 1fr; }
        .hero { padding-top: 48px; }
        .hero-card, .topic-card, .coming-soon-card, .prerequisite-toggle { padding-left: 20px; padding-right: 20px; }
        .prerequisite-content { margin: 0 10px 10px; padding: 16px; }
        .topic-card { padding-bottom: 56px; }
        .unit-divider { margin-top: 36px; }
        .brand { font-size: 1.8rem; }
      }
      @media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; } }
    

      /* COURSE NAVIGATION STATUS */
      #a-level-dropdown .dropdown-content,
      #ap-dropdown .dropdown-content {
        min-width: 300px;
      }

      #a-level-dropdown .dropdown-content a,
      #ap-dropdown .dropdown-content a,
      #a-level-dropdown .dropdown-content .dropdown-item,
      #ap-dropdown .dropdown-content .dropdown-item {
        display: flex;
        align-items: center;
        justify-content: space-between;
        gap: 12px;
        width: 100%;
        padding: 12px 16px;
        text-align: left;
      }

      #a-level-dropdown .dropdown-content .dropdown-item.is-disabled,
      #ap-dropdown .dropdown-content .dropdown-item.is-disabled {
        background: #f8fafc;
        color: #9ca3af;
        cursor: default;
      }

      .nav-coming-soon {
        flex: 0 0 auto;
        padding: 3px 7px;
        border-radius: 999px;
        background: #e5e7eb;
        color: #6b7280;
        font-size: 0.65rem;
        font-weight: 700;
        line-height: 1.2;
        white-space: nowrap;
      }

      @media (max-width: 950px) {
        #a-level-dropdown .dropdown-content,
        #ap-dropdown .dropdown-content {
          min-width: 100%;
        }
      }